FIG. 1 depicts a conventional method 10 for fabricating a structure, such as a read sensor, in a conventional microelectric device such as a read transducer. For clarity, therefore, the method 10 is described in the context of providing a read sensor in a read transducer. FIGS. 2-4 depict the conventional read transducer 30 during fabrication using the conventional method 10. FIGS. 5-6 depict plan and side views of the alternating phase shift mask (alt-PSM) 40 used in the conventional method 10. FIGS. 7-8 depict the field 50 and intensity 60 during fabrication using the conventional method 10. For clarity, FIGS. 2-8 are not to scale.
Referring to FIGS. 1-8, layers for the read sensor are fabricated on an underlying substrate, via step 12. A photoresist layer is provided on the read sensor layer(s), via step 14. The photoresist layer is assumed to be a positive photoresist, in which areas exposed to light are removed. FIG. 2 depicts the microelectric device 30 after step 14 is performed. Thus, the read sensor layers 34 reside on the underlying layer 32. The underlying layer 32 is typically an insulator, such as alumina. The read sensor layer(s) typically include more than one layer, for example reference layer(s), nonmagnetic spacer layer, and a free layer having a magnetization that may rotate in response to an external field. A photoresist layer 36 is shown on top of the read sensor layer(s).
The photoresist layer 36 is exposed using a conventional alternating phase shift mask (alt-PSM), via step 16. FIGS. 5-6 depict plan and side views of the conventional alt-PSM 40. The conventional alt-PSM 40 includes a first quartz region 42, a second quartz region 44, and a chrome line 46 between the quartz regions 42 and 44. The first quartz region 42 is thicker than the second quartz region 46. FIGS. 7-8 depict the field 50 and intensity 60 transmitted by the FIGS. 7-8 depict the field 50 and intensity 60 during fabrication using the conventional method 10 in the step 16. Because of the differences in thicknesses of the quartz regions 42 and 44, the electric field 50 is out of phase for the two sides. However, the intensity 60 is still large in these regions. In the region of the chrome line 46, no light is transmitted. Thus, the chrome line 46 corresponds to the portion of the mask layer 36 that is to remain. Because the photoresist layer was exposed in step 16, a photoresist mask is created. FIG. 3 depicts the conventional read transducer 30 after step 16 has been performed. Thus, a photoresist line 36′ has been formed. The photoresist line 36′ corresponds to the chrome line 46.
The read sensor layer(s) 34 are etched using the photoresist line 36′ as a mask, via step 18. FIG. 4 depicts the conventional read transducer 30 after step 18 has been performed. Thus, the read sensor 34′ has been defined. Fabrication of the device may then be completed, via step 20.
Although the conventional method 10 may be used for microelectric devices, such as read transducers, there are drawbacks. The method 10 and conventional alt-PSM 40 may be capable of fabricating lines having widths of approximately fifty nanometers or greater. However, the conventional method 10 using the conventional alt-PSM 40 may not be capable of adequately defining line widths of in the sub-50 nm regime. In order to fabricate structures in the sub-50 nm regime, the chrome line 46 of the alt-PSM mask 40 is required to be very thin. The manufacture of a conventional alt-PSM 40 having such a thin chrome line 46 becomes more challenging. Even if such a conventional alt-PSM 40 can be manufactured, the line width of the chrome line 46 may become less uniform. As a result, the width of the photoresist line 36′, as well as the structure being defined, may be less uniform. In semiconductor microelectric devices, a scheme utilizing chromeless phase shift lithography with assist features and off-axis illumination schemes has been proposed. However, an improved method for enhancing resolution of lithography, for example in the sub-fifty nanometer regime, is still desired.
Accordingly, what is needed is a system and method for improving the fabrication of microelectric devices, such as read transducers.